It is well known that normal clothing fabric has a tendency to become charged with static electricity which causes the clothing to cling to the wearer's body and often results in the arcing or sparking of the static electricity when the fabric is positioned in close proximity to a source of ground. The sparking or arcing of the static electricity is an annoyance to persons wearing the clothing in ordinary environments and can be extremely dangerous in certain occupations. For example, in clean room environments where electronic equipment is being manufactured and/or assembled the build-up of static electricity in the clothing can cause damage to the electronic equipment being manufactured and/or assembled.
Recognizing the inherent problem in the build-up of static electricity in clothing, many different types of anti-static fabric have been proposed in which various types of electrically conductive yarns and fibers have been incorporated to provide a controlled dissipation of static electricity into the atmosphere and to a ground.
The Webber et al U.S. Pat. No. 3,699,590 discloses a woman's slip in which an electrically conductive yarn formed of staple metal fibers may be uniformly distributed throughout the entire fabric or may be incorporated in the stitching and trim of the slip so that the static electricity is dissipated by the metallic fibers or yarns. The electrically conductive yarn is disclosed as being incorporated in woven fabric and warp and weft knit fabrics of various types with relatively low percentages of the metal fibers being incorporated in the fabric, on the order of approximately one-half to five percent. The anti-static garments disclosed in this patent are of the conventional clothing type, such as undergarments, socks and hose, sweaters, skirts, dresses, blouses, men's shorts, shirts, etc. While the garments of this patent may be suitable for conventional clothing wear to prevent a sufficient amount of static build-up to prevent the clinging of the clothing to the wearer, the garments of this patent are not satisfactory for use by workers in environments where the sparking or arcing of static electricity can cause damage to the products being worked upon.
The Thornton et al U.S. Pat. No. 4,557,968 discloses an electrostatic dissipating fabric which is illustrated as being woven, but which is described as also being knit, with a grid being formed in the fabric of electrically conductive yarns to dissipate the static electricity. The electrically conductive yarn is incorporated in the fabric in such a manner that the electrically conductive yarns form a raised grid of parallel yarns extending from one face of the fabric and extending from the front to the back surfaces of the fabric. The raised parallel grid of electrically conductive yarns extending from one face of the fabric of this patent may become snagged and pull, not only producing an unsightly appearance but may become broken and interfere with the conductive grid provided by the electrically conductive yarns incorporated in the fabric.
The above-identified patents are merely representative of the many prior art patents relating generally to the production of anti-static fabric with the incorporation therein of some type of electrically conductive yarns. Many of these prior art types of anti-static fabric have been utilized in the formation of various types of clothing and accessories for use by workers in environments where it is important to control and dissipate static electricity into the atmosphere or through a suitable grounding wire. Various types of clothing articles and accessories, such as sleeves, stool covers and the like are currently being offered for sale. Generally, anti-static clothing and accessories currently being offered can be characterized as being formed of a relatively heavy fabric, within the range of five to seven ounces per square yard, and are hot and uncomfortable for wear over the normal clothing of the worker. Also, anti-static garments of the prior art are usually woven or knit of a close construction and do not permit the free passage of air therethrough so that the usual clothing worn by the worker is not visible through the fabric forming the anti-static garment.